@tool
def calculate_shipping(
weight_kg: float,
destination_country: str,
express: bool = False
) -> dict:
"""
Calculate shipping cost for a package.
Args:
weight_kg: Package weight in kilograms (must be > 0)
destination_country: ISO 3166-1 alpha-2 country code (e.g., "US", "DE")
express: Whether to use express shipping (2-3 days vs 7-10 days)
Returns:
Dictionary with 'cost', 'currency', and 'estimated_days'
"""
...